Axiall said the incident happened in the vinyl chloride manufacturing area at the plant. The cause of the explosion is not known and the investigation is still ongoing.

An explosion at a chemical plant located near Lake Charles, in Westlake, La., injured 18 people, all of whom were treated at local hospitals. The blast occurred on Dec. 20 and caused a fire at the facility that led to an evacuation, according to the plant operator.

Axiall Corp. explained in an official statement that the incident happened in the vinyl chloride manufacturing area at the plant. The cause of the explosion is not known and the investigation is still ongoing, the company said. The fire did not have any impact on production at other parts of the chemical complex, where operations are continuing as normal.

Axiall is working with third-party independent engineering firms that are helping to assess the damage in the affected part of the plant and to ascertain whether the incident has had any long-term impact on the structure of the complex.

In its statement, the company praised the quick reaction of the plant's emergency responders, the Calcasieu Parish Sheriff's office, Louisiana State Police, Louisiana Department of Environmental Quality and the hospitals, as well as local residents. Jon Manns, plant manager at the complex, said that Axiall would like to thank everyone who responded to the fire and apologized for the "serious and unfortunate" event. Manns added that none of the workers or contractors at the facility had been seriously injured.